Re: [OSPF] OSPF Hybrid Broadcast and P2MP Interface Type

Hi Jeffrey,

please see inline:

On 23.11.2010 19:29, Jeffrey (Zhaohui) Zhang wrote:
> Peter,
>
> I think I understand the potential issue you mentioned, but not quite clear about your solution.
>
> The draft mentions that the metrics could be dynamically learned if the underlying network support it (in that case the l2 and l3 should match). However that is outside the scope the draft, which assumes that the metrics is obtained by some means. Indeed if it is statically configured then the operator needs to be careful.

dynamically updating L3 metrics based on the L2 topology is a problem of 
it own. The consequence is that L2 network changes that mostly used to 
be hidden to the L3 now becomes propagated to the L3 network.

>
> You mentioned creating p2p l2 connections. Does that mean there will be correponding l3 p2p interfaces? If yes isn't it no longer a bcast/p2mp hybrid? If not can you elaborate?

yes, some form of a sub-interface using the VLAN technology. That is 
typically a p2p connection between the two OSPF speakers.

thanks,
Peter
>
> Thanks.
> Jeffrey
>
>> -----Original Message-----
>> From: Peter Psenak [mailto:ppsenak@cisco.com]
>> Sent: Tuesday, November 23, 2010 1:11 PM
>> To: Jeffrey (Zhaohui) Zhang
>> Cc: ospf@ietf.org
>> Subject: Re: [OSPF] OSPF Hybrid Broadcast and P2MP Interface Type
>>
>> Hi Jeffrey,
>>
>> one potential issue with this approach is the possible suboptimal
>> traffic path if the L3 p2p topology created as you described do not
>> match the L2 forwarding topology. With large L2 domains it may be be
>> nontrivial to assign L3 metric correctly so that the L2/L3
>> forwarding match.
>>
>> One possible method to address the problem in hand is to create p2p
>> connections between the routers via the L2 domain, using dedicated
>> VLANs. This way the L2 forwarding is forced to match the L3
>> p2p topology.
>>
>> thanks,
>> Peter
>>
>> On 22.11.2010 17:36, Jeffrey (Zhaohui) Zhang wrote:
>>> Hi,
>>>
>>> I presented the draft
>> http://www.ietf.org/draft-nsheth-ospf-hybrid-bcast-and-p2mp-01
>> .txt in Beijing (slides
>> http://www.ietf.org/proceedings/79/slides/ospf-9.ppt) and it
>> was deferred to the mailing list on whether the problem is
>> worth the working group effort (some who reviewed the draft
>> agreed that the proposed solution is reasonable for the problem).
>>>
>>> I'd like to request folks to review the draft/slides and
>> voice your opinion. We developed the solution for a real
>> network situation and would like to see that it gets
>> consensus and standardized so that more operators/vendors can
>> benefit from this.
>>>
>>> Thanks.
>>> Jeffrey
>>> _______________________________________________
>>> OSPF mailing list
>>> OSPF@ietf.org
>>> https://www.ietf.org/mailman/listinfo/ospf
>>>
>>
>>
>